The present invention relates to sampling devices, and more particularly to devices for collecting arterial blood.
In recent years, gas analysis of arterial blood has become one of the most important laboratory tests in the management of patients with respiratory and metabolic disorders. However, the collection of a satisfactory arterial blood sample from a patient for analysis has posed a number of difficulties. Initially, in some patients it may be somewhat difficult to ascertain whether the collection device has received arterial or venous blood without measuring for the relatively high arterial pressures during collection. Second, the collection device should minimize contact of the blood sample with air since the air may affect the results of gas analysis. It is also desirable that the sample should not be collected in the presence of a vacuum, since it is believed that the vacuum may modify the gas characteristics of the sample. Finally, the device must prevent coagulation of the blood sample, and should be in a suitable form to permit closure of the sample to air and chilling during the period of time between collection and analysis.
In the past, plastic and glass syringes with a needle have been commonly used to collect the samples. However, the plastic syringes have proven deficient for such purposes due to the relatively high resistance between the syringe plunger and barrel. The plunger resistance in such plastic syringes prevents movement of the plunger responsive to arterial pressure alone, and requires that the plunger be manually withdrawn, thus creating an undesirable vacuum in the syringe chamber during collection. Further, since the plungers of plastic syringes are not sufficiently mobile to move under arterial pressure, they do not provide an indication whether arterial or venous blood is being collected. Although the plungers of the glass syringes may be used to detect arterial pressure, the glass syringes are relatively expensive, and if the nurse does not exercise sufficient care, the plunger may fall out of the syringe during arterial collection.